(U+5938): Add `<-denotational@usage' for BUCS+8A87 and BUCS+5938; add

(U+5938): Add `<-denotational@usage' for BUCS+8A87 and BUCS+5938; add
`ideographic-structure'; add `sound@ja/on/{kan|go}' and
`sound@ja/on/conventional'.
(UU+5938): Unify DJT-01963; add some relations for other characters.
(MJ009469): Unify DJT-01962.
(U-000215E2): Use `->denotational' and `->subsumptive'.
(U-00021606): Add `<-denotational@usage' for BUCS+5938.
(IU+21606): Unify DJT-01977.
(U+596E): Add `<-denotational@usage' for BUCS+596E; apply new
conventions for glyph granularity.
(U-0002D463): New character; use `<-denotational@usage' for BUCS+596E.
(BUCS+5938): New abstract node; unify A2-DJT-01963.
(BUCS+596E): New abstract node; unify A2-DJT-02019.